// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// This file provides a macro ONLY for use in testing.
// DO NOT USE IN PRODUCTION CODE.  There are much better ways to wait.

// This code is very helpful in testing multi-threaded code, without depending
// on almost any primitives.  This is especially helpful if you are testing
// those primitive multi-threaded constructs.

// We provide a simple one argument spin wait (for 1 second), and a generic
// spin wait (for longer periods of time).

#ifndef BASE_SYNCHRONIZATION_SPIN_WAIT_H_
#define BASE_SYNCHRONIZATION_SPIN_WAIT_H_

#include "base/threading/platform_thread.h"
#include "base/time/time.h"

// Provide a macro that will wait no longer than 1 second for an asynchronous
// change is the value of an expression.
// A typical use would be:
//
//   SPIN_FOR_1_SECOND_OR_UNTIL_TRUE(0 == f(x));
//
// The expression will be evaluated repeatedly until it is true, or until
// the time (1 second) expires.
// Since tests generally have a 5 second watch dog timer, this spin loop is
// typically used to get the padding needed on a given test platform to assure
// that the test passes, even if load varies, and external events vary.

#define SPIN_FOR_1_SECOND_OR_UNTIL_TRUE(expression)                   \
    SPIN_FOR_TIMEDELTA_OR_UNTIL_TRUE(base::TimeDelta::FromSeconds(1), \
        (expression))

#define SPIN_FOR_TIMEDELTA_OR_UNTIL_TRUE(delta, expression)                     \
    do {                                                                        \
        base::TimeTicks start = base::TimeTicks::Now();                         \
        const base::TimeDelta kTimeout = delta;                                 \
        while (!(expression)) {                                                 \
            if (kTimeout < base::TimeTicks::Now() - start) {                    \
                EXPECT_LE((base::TimeTicks::Now() - start).InMilliseconds(),    \
                    kTimeout.InMilliseconds())                                  \
                    << "Timed out";                                             \
                break;                                                          \
            }                                                                   \
            base::PlatformThread::Sleep(base::TimeDelta::FromMilliseconds(50)); \
        }                                                                       \
    } while (0)

#endif // BASE_SYNCHRONIZATION_SPIN_WAIT_H_
